An Australian woman used unsophisticated methods to try to conceal 18 packets of cocaine in her luggage and her family's claims she was set up are not believable, Colombian drug authorities say.

Key points:

Colombian drug police say Australian woman would have known the drugs were in the bag

Cocaine in headphones "not really a very sophisticated mode of concealment"

Cassandra Sainsbury faces up to 20 years in jail

Adelaide's Cassandra Sainsbury, 22, was arrested minutes before boarding a flight at Bogota's El Dorado International Airport with 5.8 kilograms of cocaine wrapped in plastics bags and packed within boxes of headphones.

Colonel Jorge Mendoza, the head of ports and airports for the Colombian drug enforcement police department, dismissed the family's version of events, saying she would have known the narcotics were in her bags.

"There was not really a very sophisticated mode of concealment," he said.

"The drugs were wrapped in bags, 18 packets as I said previously, inside her suitcase.

"So, it is difficult to say that she did not know that the substance was inside her suitcase."